OBJECTIVEFlow cytometry may be used to detect minimal residual disease (MRD) in acute lymphoblastic leukemia because leukemic cells often display aberrant phenotypes when compared to normal cells. The present study was designed to establish a flow cytometric method for detecting MRD in children with B-ALL and evaluate its clinical prognostic value. The investigators also aimed to study the value of the detection of MRD by flow cytometry in childhood B-ALL without effective antibody combinations.

METHODSThirty-six cases of childhood B-ALL with effective antibody combinations were performed MRD analysis after induction therapy. The authors detected MRD in 6 cases without effective antibody combinations by the four-color antibody combinations consisting of CD(45)/CD(19)/CD(10)/CD(34) and CD(45)/CD(19)/CD(20)/CD(22) and detected the aberrance of the minor subsets of CD(19)(+) cells.

RESULTS(1) Forty-two cases of childhood B-ALL were screened for antibody combinations of interest and were identified in 86% (36/42) of the cases. The sensitivity of this method was 0.01%. (2) Patients with MRD levels > or = 0.01% at 9 and 12 months of therapy had significantly low disease-free survival compared with patients with MRD levels < 0.01%. (3) Six out of seven patients with recurrence in the BM had MRD levels > or = 0.1% prior to recurrence. Patients with MRD levels > or = 0.1% during chemotherapy had significantly low disease-free survival as compared with patients with MRD values < 0.1%. (4) Two out of seven patients with recurrence had positive results of the qualitative PCR prior to recurrence. (5) Five patients with recurrence had no shift of antigen expression at relapse except that a patient missed CD(13). (6) Detectable MRD was not found in six patients without effective antibody combinations.

CONCLUSION(1) Flow cytometry is a sensitive and specific method for detecting MRD of childhood ALL, and could predict the coming relapse. (2) Patients with MRD levels > 10(-3) had poor prognosis. (3) The levels of MRD at month 9 and 12 had prognostic value. (4) The value of antibody combinations consisting of CD(45)/CD(19)/CD(10)/CD(34) and CD(45)/CD(19)/CD(20)/CD(22) should be further investigated in patients without effective antibody combinations.